Process and apparatus for treating fibrous materials for pulping purposes



May 8, 1928. 1,669,234

T. L. DUNBAR PROCESS AND APPARATUS FOR TREATING FIBROUS MATERIALS FOR PULPING PURPOSES Filed April 22. 192? 3 1g 9 Gns 2; LIQUOR LINE.

SEMco TRAP For? EAcH DIGESTER,

GHS uuouor? Eqmuzmc Tam I/z HCCUMULHTOR.

HTTORNEAY Patented May 8, 1928.

UNITED STATES PATENT OFFICE.

THOMAS L. DUNBAB, OF WATEBTOWN, NEW YORK, ASSTGINOB TO CHEIIPULP PROG- ESS, INCORPORATED, OF JEFFERSON COUNTY, NEW YORK, A CORPORATION OI NEW YORK.

PROCESS AND APPARATUS FOR TBEATING PIBIBOUS KATEBIALS I'OB PULPDI'G PURPOSES.

Application filed April 22,

One of the objects of the invention is to provide a process and apparatus which Wlll be equally as eflicient in the cooking of sulphate or soda pulp. 1 7

Another object is to furnish a process and apparatus adapted to conserve the liquor drained from the digester for reuse and conditioning, and to eliminate one washing cy cle in the'difiuser or blow tank, thereby savto hug time, chemicals and heat units.

A'further obje'ctis to provide a process and apparatus which allows the digester being used not only as a cooking device, but as a recovery'device in a novel manner.

3 With the foregoing objects Outlined and with other objects in View, which will appear as the description proceeds, the invention consists in the novel features and steps hereinafter described in detail, illustrated in 211 the accompanying drawing and more particularly pointed out in the appended claims.

In the accompanying drawing, a diagrammatic view of the improved apparatus is shown.

Referring to the drawing, i'designates a digester, 2 an equalizing tank, and 3 an accumulator. These are the main elements of the apparatus, and liquids and gases maybe circulated from one to the other, by 'means now to be described.

The upper portion of the digester is connected to a pipe 4, provided with a control valve 5, and connected to a cross-shaped fitting 6. Another pipe 7 connects the top of the digester to this fitting and is provided with a control valve 8. The fitting 6 is connected to the bottom-of the equalizing tank by a conduit 9 having a control valve ,10.

A gravity feed pipe 11 having a valve 12,

connects the equalizing tank to the intake 13 of a pump 14, and a bypass pipe 15 having a valve 16, connects the pipe 11 to the fitting 6. Y

v The outlet 17 of the pump is connected to a pipe 18 that leads'to a strainer fitting 19 at the bottom of the-digester. 1

Steam is fed into the bottom of the digester either through intakes 20 or a pipe 21 fitted with a valve 22, the parts 20 and 21 leading into the strainer fitting.

Considering the apparatus thus far described, When used in carrying out the sulphite process, it may be stated that for cock 1927. Serial No. 185,775.

ing purposes, the digester is substantially filled with chips and acid, and is properly sealed against escape ofheat or acid fumes. Steam is then introduced through the intakes 20, and this steam acts as a circulating medium for the acid through the chips, and at the same time, it builds up'the temperature and pressure within the digester.

When the temperature hasreached approximately 212 F., the valves 5, 8, 10 and 12 are opened, and thepump. 14 is started. The pump draws the acid which has in 05 creased in volume, by means of steam condensation th'rough pipes 4: and 7 through pipe 9, equalizingtank 2, and pipe 11, into the pump, and then forces the same through the pipe 18 into the bottom of the digester, thus circulating the acid through thedigester. Meanwhile, the steam entering the 'digester continues to condense and adds liquid volume, so that eventually the liquor in the equalizing tank reaches the liquor line 75 or level 23. At this time, a valve 24: in a liquor overflow pipe 25, may be opened and the liquor will flow into the Semco trap 26; When the trap is full of liquid, the automatic valve with which such traps are equipped, opens andpermits gas to flow through a pipe 27 into the trap, and by its pressure to force the liquor through a. pipe 28 into the top of the accumulator 3.

The'gas for this purpose is taken from the upper end of the equalizing tank through a pipe 29, and may be controlled by a valve 30. v 1

'As the gas accumulating in tank 2 is greater in amount than that needed to operate the trap, such gas is permitted normally to flow through a pipe 31 having a control valve 32. Pipe 31 leads the gas to a gas siphon 33' which receives liquidforced. by the pump up from pipe 18, through pipe 34. The gas and liquid are, of course, thoroughlymixed in the gas siphon, and this permits the liquid .to absorb the gas; this mixture flowing by way of pipe 35 into the intake of the pump and being circulated by the latter through the digester,'thereby enabling the pse of a weaker cooking liquor, by reasonof the fact that the gases are retained in circulation instead of being vented frgiin the digester into the usual recovery 105 ta ably it is positioned at the bottom of the digester, but the equalizing tank is prefer-' ably, ugh not necessarily, located at the op of the digester. I

From the foregoing, it will be appreciated I that when the valves are properly set, at the beginning of operation, the liquor may be simply circulated through the digester by the pump 14. However, as the volume of liquid increases, due to the addition of the condensate from the steam, this excess will be taken care of by the equalizing tank and the trap 26. Furthermore, as the gas is generated, it is mixed with liquor, re-absorbed and recirculated through the digester, so that the latter functions as a recovery device. I V

Due to this system, the heat given off by the gas in its absorption by the liquor is imparted to the latter, so that heat units are conserved.

Before the volume has become sufficient to necessitate the use of the equalizing tank, the liquor drawn by the pump 14 through the pipes 4 and 7 may be fed throu h the by-pass pipe 15 instead of throng the equalizing tank.

After the volume of liquor increases to a point where it counot be handled by the digester and-equalizing tank, the excess of liquor can be drained ofi into the accumulator. For this purpose, thedigester is provided with three valved outlets 36, 37,. and

Y 38 arranged respectively. at its top, intermediate portion and bottom, and all commu- "nicating with a pipe 39 having valves 40 and 41. This pipe communicates at its lower end with a conduit 42 which leads to the lower portion of the accumulator. Due to this arrangement, excess liquor may be passed either from the top, intermediate portion or bottom of the digester by gravity, into the accumulator. 1

Another conduit 43v having a control valve 44 connects the other end of the pipe 39 to the accumulator,-and may be used to conducteither gas or liquor from-the digester to the accumulator, or vice versa.

Liquor from the accumulator may be forcedby a pump 45 through a valved conduit 46 and a pipe 47 into the bottom of the digester, or the liquor from the pump may from' the accumulator to the digester, or

. from the digester to the accumulator.

It may be stated at this point, that'the accumulator is used to accumulate acid, alka-- line liquids, or water, and is used as a medium for the recovery of gases and heat units. In this connection, it may be noted that liquor flowing through the pipe 28 may be commingled with gas passing through the pipe 43, within the accumulator for the purpose of adding the heat units of the gas to such liquor, and for reabsorbing the gas. The digester is provided with a drain pipe 49 leading to a sewer or a storage tank.

The application of the foregoing arrangement is equally as efiicient in the cooking of sulphate or soda pulp. The eneral arrangement in cooking either of t e sulphate or soda pulps would be somewhat different than in the cooking of sulphite, in

that circulating pump 45 Would transfer the liquor showering the uncovered chips in the digester, since it is not necessar in the soda or sulphate industry; to entire y cover the chips with a liquor solution. When the apparatus is used for the latter purpose,

in the,.di'gester instead of indiffusers or blow-tanks, as heretofore, and rebuilding the pressure, in order to obtain enou h pressure to blowthe contents out of the igester. This weak liquor also gives the pulp a prewashing, whereas in the old method the contents oi the digester is blown into a diffuser, 'and the pulp soblown carries with it the liquor with'which the same has been cooked. The liquor which has been drawn back into "the accumulator is ready for reuse or reconditioning. v

As before stated, the purpose of this process is to not only better conserve the liquor" drained from the digester for reuse and conditioning, but to eliminate one washing cycle in the diffuser or blow tank, thereby saving time, chemicals and heat units. It is believed that the foregoing description, when read in connection with the accompanying drawing, will enable those skilled in the art to practice this invention, and it is obvious that changes may be made in the details set forth withoutdepartin from the spirit'of the invention as expressed in the claims. he by-pas'sed through valved pipe 48 into y by Letters Patent is:

' 1. In a chemical pulping process, chemi- What is claimed and desired to be secured cally digesting fibrous material while introducmg steam into the same, permitting the steam to condense and mix with the liquor used for digesting purposes, continuously circulating the mixed liquids through said loo fibrous material, and after the mixture reaches a predetermined volume, directing the excess of the mixed liquid into an accumulator, I

2. In a process as claimed in claim 1, withdrawing liquor and gas from the sphere of digestion after the li uor reaches a temperature of about 212 mixing the same and causing the liquid to absorb the gas,

and then circulating the gas enriched liquid through the sphere of digestion.

3. In a chemical piilping. process, digesting fibrous material with chemical liquor under super-atmospheric temperature and pressure until the'liquor reaches a temperature of about 200 F., then continuously Withdrawing chemical liquor and gas from the sphere of digestion, commingling-said l5quor andgas. and causing said liquor to absorb thelgas, and'inunediately returning the gas enriched liquor to the sphere of digestion. 3

4. In a chemical pulping process, digesting fibrous material with chemical liquor in the digester, mixing steam with said liquor in a digester and thus heating the liquor to substantially 200 F., preventing liquor from leaving the digester until the liquor has been heated to substantially 200 F, and then gradually and continuously withdrawing said liquor and gas from the sphere of digestion, mixing the withdrawn liquor and gas to cause the liquor to absorb the gas, and the latter to heat the liquor,

and immediately returning the gas enriched liquor to the sphere of digestion.

5. In a chemical pulping process, digesting fibrous material 111 a digester with chemical liquor and steam, adding condensate from the steam to the liquor until a prede-' termined volume is reached, permitting ex-- cess liquid from this mixture to gradually accumulate in a separate chamber, and uhlizing gas created during the digestion to discharge said accumulated mixed liquid in-- chemical liquor and steam, gradually draining the liquor from the digester during-the cooking so that the liquor is completely drained at the end of a cook and thus leaving the fibrous material practically free of liquor, then pumping a weak liquor solution into the drained fibrous material and thus rebuilding the pressure sufiiciently to discharge the contents out of the digester, and utilizing said weak liquor to give the pulp a prewashing.

8. An apparatus of the class'described, including a digester, .an equalizing tank, a circulating pump, pipes connecting opposite ends or the digester to the pump, pipes connecting one of the last'mentioned pipes to the equalizing tank, and valves in said pipes to permit liquid from the digester to be circulated by the pump through the equalizing 'tank or dire ctly through the pump and digester.

9. In an apparatus of the character described, a digester, a pump, pipes connecting the digester to the ump to permit the latter to circulate liquid through the digester, a mixing device, a gas conveying conduit connected to .the mixing device, another conduit connecting one of said pipes to the mixing device for leading liquid from the digester into the mixing device, and a passageway connecting the mixing device to the intake of the pump. I

10. In an apparatus of the class described, a digester, an equalizing tank, a pump, pipes connecting one end of the digester to the intake of the pump, another pipe connecting the outlet of the pump to. the other end of the digester, and valved pipes connecting the equalizing tank to certain of the other pipes to permit the pump to simultaneously circulate liquid through the digester and equalizing tank.

11. In an apparatus of the character described, a digester, an equalizing tank, a pump, a conduit connecting one end of the digesterto the equalizing tank, another conduit connecting the equalizing tank to the pump, and a third conduit connecting the pump to the other end of the digester.

12. An apparatus of the class described, including a digester, an equalizing tank, a pump, a hollow fitting, valved pipes connecting said fitting respectively to the intake of the pump, the equalizing tank and the digester, a valved pipe connecting the equalizlng tank to the intake of the pump, and another valved pipe connecting the outlet of the pump to the digester.

13. An apparatus of the class described, including a. digester, an equalizing tank, a pump, and valved pipes-connecting thedigester, equalizing tank and pump, and ar-, ranged to permit the pump to circulate liquor through the digester alone or simul- "taneously through the digesterrand equalizing tank.

-14. An apparatus as claimed in claim 13, including a gas siphon, a gas conducting conduit connecting the upper portion of the equalizing tank to said gas siphon, another conduit connecting one of said pipes to the llll ' ducting'pipes placing the equalizing tank in communicationwith the trap, and the trap in communication with the accumulator, and a gas conductingline placing the upper portion of theequalizing tank in communication with the trap for use in blowing liquor from the trap intothe accumulator. 1

17. In an apparatus of the class described a digester, an accumulator, a pump, a pipe connecting one end of the digester with one end of the accumulator, another pipe placing one end 'of the digester in'commumcation' with the accumulator, a third pipe placing said-pipes in communication, branch pipes connecting the last mentioned pipe to the digester at different elevations, another pipe placing the third pipe in communication with the accumulator, said pump being in-- terposed in one of said pipes.

18. In a chemical pulping process, chemically digesting fibrous material in a digester Wl11le introducing steam into the digester, permittingthesteam to condense and mix with the liquor used for di esting purposes,

gradually releasing heate mixed liquids from the digester after the liquids have reached a predetermined temperature, circulating the mixed liquids thus released exteriorly of the digester, and then returning a portion of the same through said fibrous material, and after the mixture reaches a predetermined volume, directing the excess of the mixed liquids into an accumulator.

19. In a chemical pulping process, chemically digesting fibrous material in a digester while introducing steam into the digester, permitting the steam to condenseand mix with the liquor used for digesting purposes, releasing heated mixed liquids and gas from the digester after the liq'uidshave reached a predetermined temperature, circulating the mixed liquids thus released exteriorly'of the digester and. simultaneously causing the mixed liquids to absorb some of the gas, then returning some of the gas enriched mixed liquids to the digester, and after the mixed liquids reaches a predetermined volume, directing the excess of the mixed liquids into an accumulator.

- 20. In a chemical pulping process, digesting fibrous material in a digester with chemical liquor whileintroducing steam into the digester, releasing gas, liquor and steam condensate substantially continuously from the digester after the liquor has reached a predetermined temperature and thereby aidmg in maintaining a substantiall constant pressure in the digester, permitting an excess proportion of the liquor and steam condensate to accumulate in an equalizing chamber while continuing the dliesting, mixing gas from the equalizing c amber with chemical liquor and steam condensate and returning'this mixture to the digester during the digestion, and discharging excess mixed liquor and steam condensate from therequalizing chamber after such mixture has reached 'a predetermined volume.

In testimony whereof, I afiix my signature at Watertown, New York, this 19th day of April, 1927.

THOMAS L. DUNBAR.

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